Recently, in terms of electric vehicles, there are needs for the implementation of environmental-friendly technologies and the solution of problems such as energy depletion and the like. Since the electric vehicles have advantages in that they operate by using a motor that outputs power by receiving electricity from a battery, no carbon dioxide is emitted, noise is very small, and energy efficiency of the motor is higher than the energy efficiency of an engine. Accordingly, electric vehicles are spotlighted as environmental-friendly vehicles.
However, unlike a conventional internal combustion engine in which cooling water is heated by using a heat source generated by an engine, there is a disadvantage in that an electric vehicle cannot heat the cooling water by using heat generated from the engine because there is no separate engine.
Therefore, a separate apparatus for heating the cooling water must be provided. A temperature sensor or a controller is typically applied to a circuit part to control the temperature of the sheath heater and to prevent it from overheating. However, when the controller or the sensor of the circuit part breaks down, it is impossible to control energization of the sheath heater, resulting in a disadvantage that the sheath heater overheats and breaks down.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.